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  #21  
Old 19-02-2021, 02:52 PM
SkyWatch (Dean)
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Hi all, I think it is important to try before you buy if you can with the 100 eyepieces: they are not for everyone!
I know this may be heresy to some, but personally I prefer a smaller apparent field; I am not that keen on having to turn my head to see the edge of the fov, which I find I have to do in most 100 eyepieces. In fact I once had a 13mm Ethos, which is a great eyepiece; but I sold it because I preferred my 13mmT6 Nagler, both in terms of the ease of the view and the size of the beast!
I have the ES 20mm, and again it is a great eyepiece, but I find that I rarely use it. It is massive, and I find I prefer the view through my 18mm Radian (which actually has an identical tfov to the 13mm Nagler!).
Others may disagree, but when I ran the 20mm ES against a 21mm Ethos in a variety of scopes (f5 dob, f4.5 dob with flattener, f8 and f6.3 refractor and f10 SCT) I could see very little difference. The Ethos was just a fraction sharper at the very edge of the field, but I couldn't see that without turning my head anyway... Both seemed equally bright and the contrast was similar.
I only paid 1/3 of the price of the Ethos for the ES (it was on a special some time back), so I see it as great value for money if you want to get into ultra wide-field viewing.

- Dean
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  #22  
Old 22-02-2021, 05:13 AM
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Quote:
Originally Posted by gregbradley View Post
Hey Don,

What's your view on native short focal length eyepieces versus Barlowing a longer focal length with a good Barlow/Powermate?

Do the look the same or do they lose a bit? I mean in general as I am sure there are lots of possible scenarios, and not all eyepieces would behave the same, but in general what would you expect?

I am thinking most likely there would be a gain going native as there would be less glass but then some eyepieces gain better correction by using a Barlow/Powermate.

Greg.
If it's a high-end Barlow, like a Baader VIP or TeleVue powerMate, there is no difference in performance between the higher power eyepiece and the Barlowed lower power eyepiece in general.
Except:
--the higher power eyepiece without a Barlow will be a lot lighter and put less stress on the focuser.
--the lower power eyepiece with a Barlow may, in some circumstances, show more light scatter or internal reflection. That depends a lot on the Barlow.
--the combination of Barlow and Eyepiece might be difficult for users of coma correctors. That stack can get very long and heavy.
--a lower power eyepiece that has induced astigmatism from fielding a short fat light cone might have less astigmatism when used in a Barlow.

I would also comment that my lifetime-best view of Jupiter was with a PowerMate (4 elements) + Paracorr (5 elements) + 8mm Ethos (9 elements). It looked like a Christopher Go or Damian Peach image, only sharper. Full technicolor, too. No more light scatter than I saw in the eyepiece by itself. Different colors on each moon, and albedo features on Ganymede. The keys: great optics and stunningly perfect seeing. Lens count? Not very important, it seems, at least with optics of that quality.
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  #23  
Old 22-02-2021, 08:25 AM
astro744
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Originally Posted by Don Pensack View Post
...

I would also comment that my lifetime-best view of Jupiter was with a PowerMate (4 elements) + Paracorr (5 elements) + 8mm Ethos (9 elements). It looked like a Christopher Go or Damian Peach image, only sharper. Full technicolor, too. No more light scatter than I saw in the eyepiece by itself. Different colors on each moon, and albedo features on Ganymede. The keys: great optics and stunningly perfect seeing. Lens count? Not very important, it seems, at least with optics of that quality.
I had a similar experience with a Tele Vue 35mm Panoptic with 4x Powermate giving me one of the finest views of Jupiter and Saturn I had ever seen. Telescope was 10.1" f6.4 Newtonian with (Suchting) refigured primary. What I liked about the view was the huge eye lens the Panoptic provides and at the higher power the Powermate offers.

What was the telescope you used your combination on, Don? I'm curious what magnification you had.

Note the Powermates are essentially invisible unless you're chasing 15th magnitude Quasars in which case a design with less but highly polished lens elements would be advantageous, (contrast is the key). I like the way the Powermates retain eye relief exactly as the original eyepiece design was intended to have.
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  #24  
Old 22-02-2021, 08:38 AM
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Originally Posted by astro744 View Post
I had a similar experience with a Tele Vue 35mm Panoptic with 4x Powermate giving me one of the finest views of Jupiter and Saturn I had ever seen. Telescope was 10.1" f6.4 Newtonian with (Suchting) refigured primary. What I liked about the view was the huge eye lens the Panoptic provides and at the higher power the Powermate offers.

What was the telescope you used your combination on, Don? I'm curious what magnification you had.

Note the Powermates are essentially invisible unless you're chasing 15th magnitude Quasars in which case a design with less but highly polished lens elements would be advantageous, (contrast is the key). I like the way the Powermates retain eye relief exactly as the original eyepiece design was intended to have.
456x in a 12.5" newtonian with Zambuto primary mirror and Antares Optics 1/30 lambda secondary in a contrast-optimized structure. Cooled with 2 large boundary layer fans and one rear fan, collimated with Glatter laser,
Farpoint Cheshire, Catseye autocollimator. PowerMate was 2X 2".
Since then, I've obtained 6mm, 4.7mm, and 3.7mm Ethos eyepieces, so I sold the PowerMate because I no longer needed it to get close to 500x.

Your experience with the 4X PowerMate doesn't surprise me.
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  #25  
Old 22-02-2021, 11:12 AM
astro744
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Originally Posted by Don Pensack View Post
456x in a 12.5" newtonian with Zambuto primary mirror and Antares Optics 1/30 lambda secondary in a contrast-optimized structure. Cooled with 2 large boundary layer fans and one rear fan, collimated with Glatter laser,
Farpoint Cheshire, Catseye autocollimator. PowerMate was 2X 2".
Since then, I've obtained 6mm, 4.7mm, and 3.7mm Ethos eyepieces, so I sold the PowerMate because I no longer needed it to get close to 500x.

Your experience with the 4X PowerMate doesn't surprise me.
Nice! I too have shorter Tele Vue f.l. eyepieces to choose from now. The 4x Powermate/35 Pan combination was heavy and is OK for high altitude viewing but anything low and I need to counterbalance. Still got the PM in case I need for photo or want to recreate the visual experience.
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  #26  
Old 23-02-2021, 08:59 PM
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Quote:
Originally Posted by Don Pensack View Post
If it's a high-end Barlow, like a Baader VIP or TeleVue powerMate, there is no difference in performance between the higher power eyepiece and the Barlowed lower power eyepiece in general.
Except:
--the higher power eyepiece without a Barlow will be a lot lighter and put less stress on the focuser.
--the lower power eyepiece with a Barlow may, in some circumstances, show more light scatter or internal reflection. That depends a lot on the Barlow.
--the combination of Barlow and Eyepiece might be difficult for users of coma correctors. That stack can get very long and heavy.
--a lower power eyepiece that has induced astigmatism from fielding a short fat light cone might have less astigmatism when used in a Barlow.

I would also comment that my lifetime-best view of Jupiter was with a PowerMate (4 elements) + Paracorr (5 elements) + 8mm Ethos (9 elements). It looked like a Christopher Go or Damian Peach image, only sharper. Full technicolor, too. No more light scatter than I saw in the eyepiece by itself. Different colors on each moon, and albedo features on Ganymede. The keys: great optics and stunningly perfect seeing. Lens count? Not very important, it seems, at least with optics of that quality.
Thanks Don.

I did some dark site viewing a few nights ago and tried the barlow out and I came to the same conclusion.

A decent barlow is a good accessory.

Greg.
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